- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Fri, 23 Sep 2005 10:34:19 -0400 (EDT)
- To: phayes@ihmc.us
- Cc: public-rdf-dawg@w3.org, connolly@w3.org, horrocks@cs.man.ac.uk, franconi@inf.unibz.it, bparsia@isr.umd.edu
Your notes have an example where a SPARQL query includes a bnode. The use of blank nodes in a SPARQL query is given two opposing meanings: Meaning 1: 2.4 Pattern Solutions Definition: Pattern Solution A pattern solution is a substitution function from a subset of the set of variables to the set of RDF terms, RDF-T. The result of replacing every v in a graph pattern P by S(v) is written S(P). If variable v is not in the domain of S then S(v) is defined to be v. Definition: Query Solution Given query Q = (GP, DS, SM, R) then S is a query solution of Q if S is a pattern solution for GP matching dataset DS. Meaning 2: 2.7 Blank Nodes Blank Nodes and Queries A blank node can appear in a query pattern. It behaves as a variable; a blank node in a query pattern may match any RDF term. Your use of blank nodes in a query corresponds to the first meaning, which, as it is the formal definition of solutions, I take to be authoritative. However, as there is a second meaning, it would be better to be very explicit as to which meaning you are using. Peter F. Patel-Schneider
Received on Friday, 23 September 2005 14:37:14 UTC